Directional antenna arrangement



y 1962 R'. MANTHEY 3,032,761

DIRECTIONAL ANTENNA ARRANGEMENT Filed June 3, 1958 2 Sheets-Sheet 1 w 4 l L I \1 ROTARY JOINT 5 T RECEIVER- TRANSMITTER lm errtan' Paula /HATl/E).

May 1, 1962 Filed June 5, 1958 RL'MANTHEY DIRECTIONAL ANTENNA ARRANGEMENT 2 Sheets-Sheet 2 APPARATUS Inventor! Pare/v7 1965M United rates Patent Ofifice 3,032,761 Patented May 1, 1962 3,032,761 EPIRECTIONAL ANTENNA ARRANGEMENT Rudr Manthey, Ulm (Danube), Germany, assignor, by

mesne assignments, to Telefunken Patentverwertungs- G.rn.b.H., Ulm (Danube), Germany Filed June 3, 1958, Ser. No. 739,489 Claims priority, application Germany June 15, 1957 3 Claims. (Cl. 343758) This invention relates to a directional antenna arrange ment for transmitting and/or receiving electromagnetic waves, more particularly for use in radar apparatus for producing different directivity patterns.

The amount of directivity of the beam depends on the particular problem to be solved. For example, when observing a given field by means of a searching radar apparatus, low azimuthal directivity is used since a wider angle of the field is always being observed at the same time. On the other hand, for closely inspecting a single object, high azimuth resolution is necessary, thisbeing only possible on condition of great directivity. Now, it may occur, in particular in radartechnique, that these two problems must be combined, i.e. when examining a field with low directivity, picking up a search object and then, closely inspecting the same. If it is not desired to employ two different antenna systems for such a combination, it is necessary to provide an arrangement whose directivity can be caused to vary rapidly by means of a simple mechanism. An arrangement wherein directivity can be varied by modifying the primary antenna, built up as a horn, is already known for solving the aforementioned problem (see Electronics, May 1955, pages 142-143). In this known arrangement the hollow feed and the horn have a rectangular cross-section; the horn height remains constant and equal to the feed height, whereas the feed width is caused vto vary linearly toward-the aperture owing to movable side walls which are hinged at the throat of the horn.

However, this known arrangement is only applicable to horn-type antennas and hasa number of other disadvantages. In first place, the directivity variation range is small;'it 'is quite insuflicient when dir'ectivity must be varied between, say, 90 and 1. Moreover, horn matching on the feed side and outwardly is generally optimum only for a predetermined aperture. Furthermore, there still appear in the horn of said known arrangement discontinuities Where light resonance occurs, thus modifying the pattern.

According to a further known arrangement, changing over between high and low directivity is provided either by means of two primary antennas having separate feeds and a different directivity and being brought selectively into the focus of a parabolic reflector, or by means of two primary antennas of different directivity arranged close to each other in the focal plane of the parabolic reflector, in the vicinity of the focus thereof. Even when disregarding the considerable drawback of the second case, namely that both antennas cannot be exactly arranged in the reflector focus and therefore undesirable, distorted patterns are bound to occur, it is obvious that with such an arrangement, directivity can only be varied within very narrow limits. Moreover, high directive antennas are only manufactured at very high costs.

In accordance with a further known arrangement, directivity variation is ensured by providing the reflector with movable parts, so that it has the surface of a para boloid for high directivity and elements of said paraboloid surface are turned out for reduced directivity. It

is however complicated to construct a paraboloid surface tional antenna arrangement for producing patterns of different directivities said arrangement comprising a directive reflector and at least one primary antenna which is so rotatably arranged that a pencil beam pattern (high directivity) is obtained when said antenna radiates toward the reflector and a fan beam pattern (low directivity) is obtained when electromagnetic, waves are transmitted and/or received by said antenna without any focusing through the reflector.

In the arrangement according to the invention, the vari ation mechanism is simple and reliable and enables for example a beam focused to in the primary antenna to be transmitted without any further focusing Or to be focused to 1 through a parabolic reflector.

Other objects, features and advantages of this invention will appear from the following description taken in con nection with the accompanying drawings. v I

FIG. 1 shows a one-antenna arrangement according to the invention providing instantaneous changeover from a fan beam to a pencil beam pattern and vice ,versa.

FIG. 2 shows the two patterns which are to be'used selectively, and I I FIG. 3 is a perspective view of another embodiment according to the invention comprising a two-antenna arrangement.

In FIG. 1 there is illustrated diagrammatically a directional antenna arrangement. Out of an apparatus (transmitter or receiver) 1 there comes a hollow feed 2 which is connected to its rotatable extension through a rotation unit 3, the axis of rotation being represented by a dotted line. The feed 2 opens into the horn-type antenna '4, which radiates either toward the reflector 5 or directly in the direction of observation (direction of the arrow, dotted line horn) by being selectively rotated about. It is of course possible to replace the horn by another primary antenna, such as a dipole, and to replace the hollow feed 2 by another conventional conductor, such as a co-axial line.

According to a further modification ofthis arrangement, the single rotating antenna may be replaced by two stationary antennas, which are mounted before the reflector on a common mechanical supporting device which also contains the feeds. One antenna radiates toward the reflector while the other transmits or receives electromagnetic waves without any focusing through the reflector. Such an arrangement is particularly room-saving as compared with an arrangement having two separate antennas, and is therefore suitable for aircraft, for example, where the length of the feeds and the bulk of the whole antenna arrangement are of consequence.

In FIG. 2 there are illustrated the two patterns which can be selectively obtained by means of the primary an tenna of the apparatus located in 1 (not shown), the pattern 2 being achieved without a reflector and the pattern 3 with a reflector.

FIG. 3 shows a perspective view of a directional antenna arrangement with two radar apparatus 6 and 7. Out of the apparatus 6 and 7 there come the hollow feeds 8 and 9 whichsupply the two primary antennas 15 and 17, respectively. In this arrangement, one of the antennas radiates toward the reflector 18 and produces a pencil beam pattern, whereas the other antenna radiates at the same time directly in the direction of observation and produces a fan beam pattern. In this preferred form of embodiment the radar apparatus 6 and 7 operate on different frequencies and the primary antennas 15 and 17 and the feeds thereof are tuned to corresponding frequency bands. Both antennas can be actuated at the same time, so that a location can be defined by a wide and a narrow pattern. The radar apparatus 6 and 7 may =3 of course be switched on selectively too, so as to produce either a narrow or a wide pattern.

With the form of embodiment of the invention illustrated in FIG. 3 it is possible to produce the fan beam and the pencil beam patterns for both frequencies employed. The radar apparatus 6 may provide a pencil beam pattern and the radar apparatus 7, a fan beam pattern (positioning shown on the drawing) or, alternatively, the radar apparatus 6, may provide a fan beam pattern and the radar apparatus 7 a pencil beam pattern. Such a switchover may be advantageous for example when one of the radar frequencies is perturbed by a jamming station. In this case, the perturbed apparatus is normally set up for searching operation with the fan beam pattern. After a coarse angular location has been obtained, a fine bearing can be achieved by switching over to the pencil beam pattern. When the first apparatus is operated with a fan beam pattern, the other apparatus may be operated with a complementary pattern for reflection location.

In order to interchange the patterns of the radar apparatus 6 and 7, there is provided a simple rotating system for the primary antennas. The feed 8 of the antenna 15 is rotatably connected to its extension 10 through a swivel member 11; in a similar manner the feed 9 of the antenna 17 is rotatably connected to its extension 11 through a swivel member 13. Both antennas can be rotated by 180 at the same time, as shown by the dotted axis A-A. Since in the present embodiment, the primary antennas lie outside the pattern focused by the reflector, so as not to disturb the beam path, the antennas-must be rotated not only about the axis A-A but also about the axis B-B when patterns are changed over. As a result thereof, the centre of radiation of the primary antenna radiating toward the reflector 18 (antenna on the drawing) is directed to the centre of said reflector, while the primary antenna operated without any further focusing (antenna 17 on the drawing) produces a horizontal directed pattern. For rotation about the axis B-B there is provided a further swivel member 14 on the feed 10 of the born 15 and also a further swivel member 16 on the feed 12 of the horn 17.

I claim:

1. A directional antenna arrangement for coupling with the transmission line of a radar system and providing radiation patterns of different beam widths, comprising in combination: primary antenna means having a relatively broad primary radiation pattern; reflector means operatively disposed opposite said antenna means and cooperating therewith for providing a sharply focussed secondary pattern; and rotary joint means for electrically coupling said antenna means to said transmission line and permitting said antenna means to be selectively rotated mechanically between a first position in which said antenna means directs its primary radiation pattern into said reflector means thereby providing the sharply focussed secondary pattern, and a second position in which said antenna means directs its primary radiation pattern away from said reflector means but in the same direction as the secondary pattern thereof.

2. The arrangement as set forth in claim 1, wherein said primary antenna means comprises two antenna devices coupled to transmission lines and operating at different frequencies, and said rotary joint means permitting a selected one of said antenna devices to direct its pattern into said reflector means while, at the same time, directing the pattern of the other antenna device away from the reflector means and in the same direction as the pattern thereof.

3. The arrangement as set forth in claim 2, wherein said antenna devices are respectively located back-to-back and offset from the secondary beam of the reflector means, and wherein said rotary joint means comprise two joints joining each antenna device to a transmission line, whereby the mutual positions of the antenna devices can be reversed in one plane and the axis of the antenna means facing the reflector means can be inclined with respect to the axis of the other antenna device to compensate for its offset from the reflector means.

References Cited in the file of this patent UNITED STATES PATENTS 1,932,469 Leib et a1 Oct. 31, 1933 2,423,073 Willoughby June 24, 1947 2,473,421 Fubini et a1 July 14, 1949 2,514,617 Albersheim July 11, 1950 2,521,732 Kline Sept. 12, 1950 2,633,533 Robinson Mar. 31, 1953 2,716,746 Howery Aug. 30, 1955 2,842,766 Hutchison et al July 8, 1958 2,913,723 Thourel Nov. 17, 1959 OTHER REFERENCES Antennas, John D. Kraus, published by McGraw-Hill Book Co., 1950, page 340. 

